This application claims the priority of Japanese Patent Application No. 11-83990 filed on Mar. 26, 1999, which is incorporated herein by reference.
The present invention relates to a titanium-silica complex and, in particular, to an improvement in properties of titanium dioxide which has ultraviolet protective ability.
Sunburn is caused by the relation between the light of 280 to 400 nm, which reaches on the ground, among ultraviolet ray and light sensitivity of the skin. Sunscreen cosmetic preparations that comprise UV-absorber or UV-screening agent exist in order to prevent sunburn. Sunscreen cosmetic preparations can demonstrate their effect by applying them onto the skin.
In the region of ultraviolet ray which melanize the skin, the ultraviolet ray of 280 to 320 nm that is called UV-B produces erythema and also produces melanization after producing erythema. To the contrary, the ultraviolet ray of 320 to 400 nm that is called UV-A directly produces melanization without producing erythema. Some cosmetic preparation may achieve absorption and screening of such ultraviolet ray by compounding organic materials. In recent years, however, it is mainstream that the cosmetic preparations which obtain such effects by adding inorganic powders that is stable with respect to light and have small influence on the human body.
As inorganic powders, zinc oxide, titanium oxide and the like are exemplified. The refractive index of titanium oxide is 2.3 to 2.6 and is highest among pigments. Hiding power of titanium oxide is also greatest among white pigments and is two times to three times of zinc oxide. In the actual sunscreen cosmetic preparation, however, it is desirable to prevent sunburn with making the application of the inorganic powder inconspicuous.
Accordingly, the sunscreen cosmetic preparations which compound ultrafine titanium oxide that is inconspicuous in whiteness as compared with pigment class titanium oxide and which have natural finishing and excellent ultraviolet absorbing ability have been developed recently.
However, when the particle diameter of titanium dioxide is cut into smaller pieces, oil absorption is increased because of expansion of specific surface area. Consequently, dispersibility of base system in cosmetic preparation is deteriorated and ultraviolet ray transmission rate also receives bad influence.
Amelioration of dispersibility for base system and ultraviolet protective ability can be demonstrated by making titanium dioxide to spindle shape. However, it is not always found so much amelioration with respect to transparency.
The present invention is achieved in view of the foregoing problems, an object of the present invention is to provide a complex which is excellent in transparency and protective ability of UVB region by containing titanium oxide in a specific silica carrier.
Another object of the present invention is to provide a cosmetic preparation which has natural finishing i.e., excellent in transparency by the complex and is excellent in protective ability of UVB region.
In order to achieve the foregoing object, a titanium-silica complex in accordance with the present invention comprises a silica carrier and titanium oxide, wherein said silica carrier is mainly composed of silicon oxide and wherein titanium oxide is contained in said silica carrier.
Also, in the present invention, it is preferable that plurality of a fine titanium oxide particle is incorporated in said silica carrier in the dotted form that has almost homogeneous density.
Also, in the present invention, a complex of silicon oxide and titanium oxide that is obtained by including titanium oxide is preferable in case of depositing silicon oxide.
Also, in the present invention, a complex of silicon oxide and titanium oxide that is obtained by including a precursor of titanium oxide is preferable in case of depositing silicon oxide.
Also, in the present invention, a complex of silicon oxide and titanium oxide that is obtained by including titanium oxide is preferable in case of depositing a silicate.
Also, in the present invention, a complex of silicon oxide and titanium oxide that is obtained by including a precursor of titanium oxide is preferable in case of depositing a silicate.
Also, in the present invention, it is preferable that an additive concentration of titanium oxide is 0.5 to 90% with respect to the whole mass of the powder.
A cosmetic preparation in accordance with the present invention compounds any one of the titanium-silica complexes as mentioned hereinbefore.